求助List

[人在風雨中]

[叫练]

import java.util.*;
import java.util.stream.Collectors;

/**
 * @author ：jiaolian
 * @date ：Created in 2021-01-13 14:04
 * @description：订单分组测试
 * @modified By：
 * 公众号:叫练
 */
public class OrderByGroupTest {
    public static void main(String[] args) {

        //创建订单;
        List<Order> list = new ArrayList();
        list.add(new Order("176",1700));
        list.add(new Order("885",4400));
        list.add(new Order("885",5100));
        list.add(new Order("664",5000));
        list.add(new Order("664",2500));
        list.add(new Order("481",3000));

        //将list按oid分组
        Map<String,List<Order>> listMap = list.stream().collect(Collectors.groupingBy(Order::getOid));

        //输出测试；
        Set<Map.Entry<String,List<Order>>> set =  listMap.entrySet();
        Iterator<Map.Entry<String,List<Order>>> iterator = set.iterator();
        while (iterator.hasNext()) {
            Map.Entry entry = iterator.next();
            System.out.println("key:"+entry.getKey()+" val:"+entry.getValue());
        }


    }

    //TODO 简化订单对象
    private static class Order {
        //订单id
        private String oid;
        //价格
        private double price;

        public Order(String oid, double price) {
            this.oid = oid;
            this.price = price;
        }

        public String getOid() {
            return oid;
        }

        public void setOid(String oid) {
            this.oid = oid;
        }

        public double getPrice() {
            return price;
        }

        public void setPrice(double price) {
            this.price = price;
        }

        @Override
        public String toString() {
            return "Order{" +
                    "oid='" + oid + '\'' +
                    ", price=" + price +
                    '}';
        }
    }
}

简化了订单表Order，代码用到JDK1.8新特性List流化，一行代码就可以搞定将list分组，1.8以前需要通过订单id分组成list，然后把list再放入Map。下面是测试结果，如果对你有用，请给个关注哦！

[啥都无所谓]

group by 你的 id ，把所有id查出来，再循环遍历去取出来。取出来的不就是一样的了吗？

[廾匸随笔]

引用 1 楼 叫练 的回复:

import java.util.*;
import java.util.stream.Collectors;

/**
 * @author ：jiaolian
 * @date ：Created in 2021-01-13 14:04
 * @description：订单分组测试
 * @modified By：
 * 公众号:叫练
 */
public class OrderByGroupTest {
    public static void main(String[] args) {

        //创建订单;
        List<Order> list = new ArrayList();
        list.add(new Order("176",1700));
        list.add(new Order("885",4400));
        list.add(new Order("885",5100));
        list.add(new Order("664",5000));
        list.add(new Order("664",2500));
        list.add(new Order("481",3000));

        //将list按oid分组
        Map<String,List<Order>> listMap = list.stream().collect(Collectors.groupingBy(Order::getOid));

        //输出测试；
        Set<Map.Entry<String,List<Order>>> set =  listMap.entrySet();
        Iterator<Map.Entry<String,List<Order>>> iterator = set.iterator();
        while (iterator.hasNext()) {
            Map.Entry entry = iterator.next();
            System.out.println("key:"+entry.getKey()+" val:"+entry.getValue());
        }


    }

    //TODO 简化订单对象
    private static class Order {
        //订单id
        private String oid;
        //价格
        private double price;

        public Order(String oid, double price) {
            this.oid = oid;
            this.price = price;
        }

        public String getOid() {
            return oid;
        }

        public void setOid(String oid) {
            this.oid = oid;
        }

        public double getPrice() {
            return price;
        }

        public void setPrice(double price) {
            this.price = price;
        }

        @Override
        public String toString() {
            return "Order{" +
                    "oid='" + oid + '\'' +
                    ", price=" + price +
                    '}';
        }
    }
}

简化了订单表Order，代码用到JDK1.8新特性List流化，一行代码就可以搞定将list分组，1.8以前需要通过订单id分组成list，然后把list再放入Map。下面是测试结果，如果对你有用，请给个关注哦！

你这拉关注的成本也太高了吧兄弟

[叫练]

10分钟的事情，还行吧，帮助是美德，关注是缘分。一切随缘